There are a lot of Laos approvals in the threads which will help. Many accounts detail the interview as brief, you will need to show your 500k in your account on your phone. Approvals are quickly given post interview.
When you return from your trip you will be given a fresh 180-day stamp. Best to have evidence of your course enrolment to hand on arrival just in case of being asked, especially if entering via Chiang Mai. Overwhelming majority have no issue reentering.,
Anonymous participant Docs in the language of the embassy you are applying may be acceptable, but you have to check. Which embassy are you applying from?